The leak was spectacularly bad timing for Pakistan's Foreign Minister Hina Rabbani Khar, who was in Kabul for the first time since taking office last year in a bid to thaw frosty ties between the two neighbours.

"We have no hidden agenda in Afghanistan," Khar told reporters after meeting President Hamid Karzai. "These claims have been made many, many times. Pakistan stands behind any initiative that the Afghan government takes for peace."

The Taliban chose the same day to deny that they would soon hold talks with Karzai's government in Saudi Arabia to end the decade-long war since they were toppled by a US-led invasion in 2001.

"There is no truth in these published reports saying that the delegation of the Islamic Emirate would meet with representatives of the Karzai government in Saudi Arabia in the near future," the Taliban said on their website.

Afghan officials had suggested that talks in Saudi Arabia would be in addition to contacts in Qatar between the Taliban and the United States.

But it was never clear whether the Taliban, who have resisted talks with the Afghan government, or the Saudis, who have conditioned involvement on the Taliban renouncing al-Qaeda, would come on board.

Taliban negotiators have begun preliminary discussions with the United States in Qatar on plans for peace talks aimed at ending the war.

But they said in their statement on Wednesday that they had not yet "reached the negotiation phase with the US and its allies".

"Before there are negotiations there should be a trust-building phase, which has not begun yet," the statement said.

One of the Taliban's demands is for the United States to free five of its leaders from detention in the US military prison in Guantanamo Bay.

The leaked Nato report – seen by The Timesnewspaper and the BBC – was compiled from information gleaned from insurgent detainees and was given to Nato commanders in Afghanistan last month.

The "State of the Taliban" document claims that Islamabad, via Pakistan's ISI intelligence agency, is "intimately involved" with the insurgency and that the Taliban assume victory is inevitable once Western troops leave in 2014.

The Times quoted the report as saying the Taliban's "strength, motivation, funding and tactical proficiency remains intact", despite setbacks in 2011.

"Many Afghans are already bracing themselves for an eventual return of the Taliban," it said.

Nato's International Security Assistance Force (ISAF), however, appeared to distance itself from the contents of the document.

The document "may provide some level of representative sampling of Taliban opinions and ideals but clearly should not be used as any interpretation of campaign progress", spokesman Lieutenant Colonel Jimmie Cummings told AFP.

Pakistan's foreign minister said: "We consider any threat to Afghanistan's independence and sovereignty as a threat to Pakistan's existence.

"Pakistan and Afghanistan need to look forward to a relationship based on trust."

Afghan Foreign Minister Zalmai Rasoul told the same news conference: "There will be no peace in the region if there is no serious regional co-operation.

"Pakistan plays a key role in Afghan peace process. I hope Ms Rabani's visit is the beginning of a good relationship between our two countries."